1. Field of the Invention
The present invention relates to a laser beam projector. More specifically, the present invention relates to a laser beam projector capable of being incorporated into an automatic welding head held on the free end of a robot arm or the like and of projecting a laser beam accurately on a portion to be welded.
2. Description of the Related Art
Butt welding using a laser beam is used prevalently for welding members in order to manufacture automobiles, etc. Recently, CO2 lasers have been replaced by YAG lasers capable of focusing a laser beam in a spot smaller than that which is formable by CO2 lasers. A welding process using a YAG laser capable of focusing a laser beam in a small spot is able to achieve fine welding using a small laser-beam spot. Incidentally, fine welding requires forming the laser-beam spot at a groove in a positional accuracy on the order of 0.05 mm.
However, the tracing accuracy of the current industrial robot is not high enough to meet the aforesaid positioning accuracy. Therefore, satisfactory welding meeting the required welding accuracy cannot be achieve simply by mounting a YAG laser beam projector on the free end of a robot arm and making the robot arm trace a weld line taught beforehand to the industrial robot. Various measures have been proposed to meet the required welding accuracy.
A laser beam machine described in JP-A 328867/1998 comprises a work table for holding a tensioned plate-shaped workpiece and axially moving the workpiece, a laser beam machining head including an optical focusing system for focusing a laser beam and capable of axial movement for focusing a laser beam on the workpiece, an upper workpiece holding member integrally provided with a laser beam projecting nozzle, a hollow, expansion connecting member interconnecting the laser beam machining head and the upper workpiece holding member such that the laser beam machining head and the upper workpiece holding member can be moved relative to each other for focusing the laser beam, and a lower stationary surface plate. The workpiece is held between the upper workpiece holding member and the lower stationary surface plate at a position near a laser beam machining position.
This known laser beam machine moves the work table supporting the workpiece thereon to make the laser beam trace a desired path. Therefore, the laser beam machine is inevitably large and is subject to restrictions on the shape of the workpiece.
The present invention has been made in view of the foregoing problem and it is therefore an object of the present invention to provide a laser beam projector capable of being mounted on an automatic welding machine, such as a welding robot, of assisting the operation of the automatic welding machine and of projecting a laser beam on a portion to be welded in a high accuracy.
According to the invention, a laser beam projector comprising: an optical head that projects a laser beam; and a holding-turning mechanism that holds and turns the optical head.
Preferably, holding-turning mechanism holds the optical head so that the optical head is able to turn about an axis passing a center of gravity of the optical head.
Preferably, the holding-turning mechanism includes a first holding-turning unit that turns the optical head in a direction perpendicular to a weld line and a second holding-turning unit that turns the optical head in a direction of the weld line.
Preferably, the holding-turning mechanism includes a turning link mechanism that transmits a driving force to the optical head in order to turn the optical head.
The optical head may be a head which emits a YAG laser beam.
The optical head may be mounted on a robot arm, and so on.